Liquid crystal display with particular reflective switched states

ABSTRACT

A liquid crystal display device is made by disposing an STN cell ( 16 ) in which nematic liquid crystal ( 6 ) having a twist angle in the range from 180° to 270° is filled and sandwiched between a first substrate ( 1 ) having a first electrode ( 3 ) and a second substrate ( 2 ) having a second electrode ( 4 ) at the center, providing a retardation film ( 13 ) and an absorption-type polarizing film ( 8 ) outside the second substrate ( 2 ) in order, and providing a reflection-type polarizing film ( 10 ) and a light absorbing film ( 11 ) outside the first substrate ( 1 ) in order. This enables a metallic silver background due to the reflected light by the reflection-type polarizing film ( 10 ) and display in black or in color by light passing through the reflection-type polarizing film ( 10 ) being absorbed in the light absorbing film ( 11 ) or only light of specific color being reflected.

TECHNICAL FIELD

The present invention relates to a liquid crystal display device,particularly to a monochromatic color liquid crystal display device inwhich a background portion of a display and a display portion ofletters, figures and the like are colored.

BACKGROUND TECHNOLOGY

Conventionally, several means have been proposed for a monochromaticcolor liquid crystal display device of which a background portion of adisplay and a display portion of letters, figures and the like arecolored in a liquid crystal display device.

The first conventional art is a monochromatic color liquid crystaldisplay device in which a color polarizing film is provided outside aliquid crystal display panel, which is simple in structure and generallyused.

The second conventional art is a monochromatic color liquid crystaldisplay device in which nematic liquid crystal in a liquid crystal cellforming a liquid crystal display panel is mixed with a dichromaticpigment which is allowed to move together with the movement of thenematic liquid crystal molecules, which is referred to as a guest-hostscheme.

However, in any one of the conventional monochromatic color liquidcrystal display devices, letters and figures colored with a dye or adichroic pigment are displayed in a white background, or conversely,white letters and white figures are displayed in a background coloredwith a dye or a dichroic pigment, which makes the contrast thereof low.Furthermore, the number of the dyes or the dichroic pigments is limited,which causes a disadvantage in that the number of colors usable fordisplaying is limited.

Additionally, a liquid crystal display device which is suitable forcolorful designs, capable of a metallic display, and excellent in avisible angle characteristic is required for a digital watch or aportable telephone.

The present invention is invented in view of the present situation andits object is to provide a liquid crystal display device in which colorletters and color figures are displayed in a metallic background, orconversely, metallic letters and figures are displayed in a colorfulbackground, and thereby a display with high contrast and richness indesigns is possible, and the viewing angle characteristic is alsoexcellent.

DISCLOSURE OF THE INVENTION

In order to achieve the above objects, the liquid crystal display deviceaccording to the present invention is made as described hereinafter.

In the liquid crystal display device, used is a super twisted nematic(STN) liquid crystal cell which is made by filling and sandwichingnematic liquid crystal, having a twist angle in the range from 180° to270°, between a transparent first substrate having a first electrode anda transparent second substrate having a second electrode.

A retardation film is provided outside the second substrate of the STNliquid crystal cell and an absorption-type polarizing film which absorbsthe light linearly polarized in the direction orthogonal to thetransmission axis thereof is provided outside the retardation film.Furthermore, a reflection-type polarizing film which reflects the lightlinearly polarized in the direction orthogonal to the transmission axisthereof is provided outside the first substrate of the STN liquidcrystal cell described above and a light absorbing member is providedoutside the reflection-type polarizing film.

As the retardation film, used is a retardation film having relations ofnx>nz>ny, where nx is the refractive index in the direction of the phasedelay axis, ny is the refractive index in the Y-axis direction, and nzis the refractive index in the thickness direction.

Alternatively, a twisted retardation film is provided outside the secondsubstrate of the STN liquid crystal cell and the absorption-typepolarizing film is provided outside the twisted retardation film, andthe reflection-type polarizing film and the light absorbing member maybe provided outside the first substrate of the STN liquid crystal cell,in order.

Preferably, in the liquid crystal display devices, a light diffusionlayer may be provided on the outside surface of the absorption-typepolarizing film or a light diffusion sheet may be provided outside theabsorption-type polarizing film.

The absorption-type polarizing film can be a color retardation filmusing a dichroic pigment.

The light absorbing member can be a color filter or a solar cell.

Alternatively, the light absorbing member can be a translucent absorbingmember and a back light can be provided outside the translucentabsorbing member.

A light diffusion layer can be also provided between the first substrateof the STN liquid crystal cell and the reflection-type polarizing film.

Through the above configuration, in the liquid crystal display deviceaccording to the present invention, a metallic silver background due tothe light reflected by the reflection-type polarizing film and displayin black or in color with excellent contrast by means of light passingthrough the reflection-type polarizing film being absorbed in the lightabsorbing member or only light of specific color being reflected arepossible. Note that the detailed operations will be described in theembodiments of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view showing a structure of afirst embodiment of a liquid crystal display device according to thepresent invention;

FIGS. 2 and 3 are plane views showing positional relations of axes ofthe liquid crystal display device;

FIG. 4 is an explanatory perspective view for explaining a coloringmechanism of the liquid crystal display device in a first embodiment;

FIG. 5 to FIG. 10 are schematic cross-sectional views showing respectivestructures of a second embodiment to a seventh embodiment of the liquidcrystal display device according to the present invention;

FIG. 11 is a schematic cross-sectional view showing a structure of aeighth embodiment of the liquid crystal display device according to thepresent invention;

FIGS. 12 and 13 are plane views showing positional relations of axes ofthe liquid crystal display device in an eighth embodiment;

FIG. 14 to FIG. 19 are schematic cross-sectional views showingrespective structures of a ninth embodiment to a fourteenth embodimentof the liquid crystal display device according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out a liquid crystal display device accordingto the present invention will be described hereinafter with reference tothe drawings.

First Embodiment: FIG. 1 to FIG. 4

The first embodiment of the liquid crystal display device according tothe present invention will be explained first with reference to FIG. 1to FIG. 4. FIG. 1 is a schematic cross-sectional view showing astructure of the liquid crystal display device, in which the thicknessof members and the gaps between thereof are shown substantiallyenlarged. FIGS. 2 and 3 are plane views showing positional relations ofeach axis of the components.

The liquid crystal display device is structured, as shown in FIG. 1, insuch a manner that a first substrate 1 and a second substrate 2, whichare both made of glass plates with a thickness of 0.5 mm, are adhered toeach other through a sealing member 5 provided at the periphery thereof,and nematic liquid crystal 6 which is aligned at a twist angle of 225°is filled and sandwiched in a gap between the pair of the substrates 1and 2 to form a super twisted nematic (STN) liquid crystal cell 16. Onthe inner side of the first substrate 1, a transparent first electrode 3is formed with Indium Tin oxide (ITO) and on the inner side of thesecond substrate 2, a transparent second electrode 4 is also formed withITO.

One of the first and second electrodes 3 and 4 is a display electrode,which is formed into a display pattern, or a pattern (matrix) ofsegments or dots (pixels). The other is a counter electrode, which isformed into a common whole surface pattern or a belt-shaped pattern inlines or rows.

On the surfaces of both the first electrode 3 and the second electrode4, formed is an alignment film (not shown).

As shown in FIG. 2, on the first substrate 1 side, a rubbing treatmentis performed so that a lower molecular alignment direction 16 a ofliquid crystal of the nematic liquid crystal 6 is disposed in thedirection rotated 22.5° counterclockwise with respect to a horizontalaxis 30 (0°). On the second substrate 2 side, a rubbing treatment isperformed so that an upper molecular alignment direction 16 b of liquidcrystal of the nematic liquid crystal 6 is disposed in the directionrotated 22.5° clockwise with respect to the horizontal axis 30 (0°).Through the above structure, formed is the STN liquid crystal cell 16 inwhich the twisted alignment angle of the nematic liquid crystal 6 is225° counterclockwise seen from the second substrate 2 side.

A difference Δn in birefiingence of the nematic liquid crystal 6 usedfor the STN liquid crystal cell 16 is set to be 0.15 and a cell gap dwhich is a gap between the first substrate 1 and the second substrate 2is set to be 5.5 μm. Accordingly, a Δnd value of the STN liquid crystalcell 16 which is represented by the product of the difference Δn in thebirefringence of the nematic liquid crystal 6 and the cell gap d is 825nm. A twisted pitch of the nematic liquid crystal 6 is adjusted to 11μm.

A retardation film 13 is provided outside (on the visible side of) thesecond substrate 2 of the STN liquid crystal cell 16 and anabsorption-type polarizing film 8 is provided outside the retardationfilm 13. Furthermore, a reflection-type polarizing film 10 is providedoutside (on the opposite side to the visible side of) the firstsubstrate 1 and a light absorbing film 11 is provided outside thereflection-type polarizing film 10 to form the liquid crystal displaydevice (panel).

The absorption-type polarizing film 8 is a polarizing film or sheetwhich transmits the light linearly polarized in the direction parallelto the transmission axis thereof and absorbs the light linearlypolarized in the direction orthogonal to the transmission axis thereof.

The absorption-type polarizing film 8 is a commonly used polarizing filmwhich is made by a stretched film being dyed with iodine or a dichroicpigment.

The reflection-type polarizing film 10 is a polarizing film or sheetwhich transmits the light linearly polarized in the direction parallelto the transmission axis thereof and reflects the light linearlypolarized in the direction orthogonal to the transmission axis thereof.

As the reflection-type polarizing film 10, which is made by thin filmsbeing formed on a transparent base film in multi-layered structure, forinstance, Optical Film D-BEF (trade name) sold by Sumitomo 3M Co. Ltd.is used.

D-BEF is a product to be used typically for raising the luminance of aback light and serves sufficiently as the reflection-type polarizingfilm in the embodiment.

The retardation film 13 serves as a birefringence layer and a biaxialstretching film or a uniaxial stretching film can be used for thepurpose.

In this embodiment, for improving the viewing angle characteristic, abiaxial retardation film having relations of nx>nz>ny, where nx is therefractive index in the direction of the phase delay axis (a stretchingdirection), ny is the refractive index in the Y-axis direction (adirection orthogonal to the direction of the phase-delay axis) and nz isthe refractive index in the thickness direction, is used. Naturally, auniaxial retardation film may be used.

However, the viewing angle characteristic is further improved by using abiaxial retardation film. Since incident light from all directions isutilized, this is preferable because a reflection-type liquid crystaldisplay device becomes brighter.

The absorption-type polarizing film 8 is structured in such a mannerthat a transmission axis 8 a shown in FIG. 3 is disposed at an angle of−70° with respect to the horizontal axis 30 (0°) and the retardationfilm 13 with the retardation value of 590 nm is disposed between the STNliquid crystal cell 16 and the absorption-type polarizing film 8, with aphase delay axis 13 a thereof being at an angle of 50° with respect tothe horizontal axis 30.

The reflection-type polarizing film 10 under the STN liquid crystal cell16 is disposed in such a manner that a transmission axis 10 a shown inFIG. 2 is at an angle of 75° with respect to the horizontal axis 30.Under the reflection-type polarizing film 10, disposed is a sheet of redpaper as the light absorbing film 11.

The STN liquid crystal cell 16 and the reflection-type polarizing film10 are adhered to each other with acrylic adhesives. The absorption-typepolarizing film 8, the retardation film 13 and the STN liquid crystalcell 16 are also adhered to each other with acrylic adhesives.

As the absorption-type polarizing film 8, a common one to which nodiffusion surface treatment is performed is used. Accordingly, a displayin which the surface reflects light like a mirror and in which themetallic appearance is emphasized can be obtained.

Hereinafter, the mechanism of a monochromatic color display by theliquid crystal display device of the first embodiment will be explainedwith reference to FIG. 4.

The right in FIG. 4 shows an “off-state” in which voltage is not appliedacross the first and second electrodes 3 and 4 of the STN liquid crystalcell 16, and the left shows an “on-state” in which voltage is appliedrespectively.

Out of the natural light incident from the upper side (visible side)onto the liquid crystal display device in FIG. 4, only the lightlinearly polarized in the direction parallel to the transmission axis 8a of the absorption-type polarizing film 8 passes through theabsorption-type polarizing film 8. The light linearly polarized in thedirection parallel to an absorbing axis 8 b orthogonal to thetransmission axis 8 a is absorbed in the absorption-type polarizing film8.

The linearly polarized light passed through the absorption-typepolarizing film 8 reaches the retardation film 13 and is affected by abirefringence action while it passes through the retardation film 13 tobe in an elliptically polarized state.

When the STN liquid crystal cell 16 is in an off-state (the right inFIG. 4), the elliptically polarized light is compensated during passagethrough the STN liquid crystal cell 16 to be a substantially linearlypolarized light, and is rotated about 55° with respect to thetransmission axis 8 a of the absorption-type polarizing film 8 to emitfrom the position at −15° with respect to the horizontal axis 30 in FIG.3.

The reflection-type polarizing film 10 is disposed in such a manner thatthe transmission axis 10 a thereof is in the direction of 75°counterclockwise with respect to the horizontal axis 30 as shown in FIG.2. Accordingly, the linearly polarized light passed through the STNliquid crystal cell 16, of which the direction of the polarization is inthe direction twisted by 90° (orthogonal) with respect to thetransmission axis 10 a of the reflection-type polarizing film 10, isthus all reflected by the reflection-type polarizing film 10. Thereflected light passes back to emit to the visible side, therefore thebackground becomes metallic silver.

On the other hand, in an on-state (the left in FIG. 4) where voltage isapplied across the first electrode 3 and the second electrode 4 of theSTN liquid crystal cell 16, molecules of the nematic liquid crystal 6rise, the birefringence of the STN liquid crystal cell 16 changes, thelinearly polarized light passing through the STN liquid crystal cell 16rotates about 90° to be in the direction of 75° counterclockwise withrespect to the horizontal axis 30 in FIG. 2.

Accordingly, the linearly polarized light incident onto thereflection-type polarizing film 10, of which the direction of thepolarization becomes parallel to the transmission axis 10 a of thereflection-type polarizing film 10, thus all passes through thereflection-type polarizing film 10 and is absorbed in the lightabsorbing film 11. A sheet of red paper is used as the light absorbingfilm 11, therefore red light is reflected and passes back to emit to thevisible side. Thus a red display can be obtained.

As described above, according to this liquid crystal display device,information with letters and figures can be displayed in color on ametallic silver background, and enough contrast and an excellent viewingangle characteristic can be obtained. Moreover, the STN liquid crystalcell is used as a liquid crystal cell, thereby the nematic liquidcrystal molecules sharply change in accordance with the applied voltageand so the shapeness in the optical characteristic can be improved.

Thus, the number of scanning lines can be increased up to 100 to 400lines even in a scanning by simple-matrix driving, accordingly, alarge-scale liquid crystal display device and a high-density liquidcrystal display device can be provided. The viewing angle characteristicis also improved.

Modification of the First Embodiment

In the aforesaid first embodiment, the use of red paper as the lightabsorbing film 11 results in the liquid crystal display device toperform a red display on a metallic silver background. The color tone ofthe liquid crystal cell in the on-state can be optionally changed bychanging the material of the light absorbing film 11.

For example, the use of a black film as the light absorbing film 11makes a black display, the use of a blue color filter makes a bluedisplay, and the use of gold paper makes a gold display. Accordingly,information with letters, figures and the like can be displayed in arequired color on the metallic silver background, and various designscan be realized.

In this embodiment, a metallic silver background is displayed in a statewith no voltage applied and a color display in a state with applicationof voltage on the STN liquid crystal cell. If the reflection-typepolarizing film 10 is disposed in a manner such that the transmissionaxis 10 a thereof is rotated by 90° to be at an angle of −15° withrespect to the horizontal axis 30 in FIG. 2, it is also possible that acolor background is displayed in the state with no voltage applied and ametallic silver display in the state with application of voltage on theSTN liquid crystal cell 16.

Furthermore, in this embodiment, an ordinary polarizing film in whichstretched PVA (polyvinyl alcohol) is dyed with iodine and sandwichedbetween TAC (triacetyl cellulose) films is used as the absorption-typepolarizing film 8. The use of a colored polarizing film in whichstretched PVA is dyed with a dichromatic pigment and sandwiched betweenTAC films as the absorption-type polarizing film 8 enables the metallicsilver background to be colored.

The liquid crystal display device in which letters and figures aredisplayed in red on a blue metallic background can be manufactured byreplacing the absorption-type polarizing film 8 shown in FIG. 1 with ablue color polarizing film.

Moreover, in the first embodiment, while the STN liquid crystal celltwisted by 225° is used as the STN liquid crystal cell 16, the sameeffects can be obtained if the twisted angle of STN liquid crystal cellis in the range of 180° to 270°.

Furthermore, in the first embodiment, a single retardation film 13 isused for making the linearly polarized light which passed through theabsorption-type polarizing film 8 be in an elliptically polarized state,and the use of a plurality of retardation films 13 enables morecompletely elliptically polarized state to be realized, and enables thequantity of light which is returned as the linearly polarized light andtwisted by the STN liquid crystal cell 16 to be increased, so that amore vivid metallic silver background and color display can be obtained.

In this case, a plurality of retardation films may be disposed on oneside of the STN liquid crystal cell 16 or may be disposed separately onboth sides of the STN liquid crystal cell 16.

Second Embodiment: FIG. 5

FIG. 5 is a schematic sectional view showing a structure of the secondembodiment of the liquid crystal display device according to the presentinvention. The same numerals are given to the same portions as those inFIG. 1 and so the descriptions thereof will be omitted. The structure ofthe STN liquid crystal cell 16 is the same as that of the firstembodiment shown in FIG. 1 and so the drawing is simplified. The samesituation and condition are applied to FIG. 6 through to FIG. 10hereinafter.

The liquid crystal display device of the second embodiment differs fromthe liquid crystal display device shown in FIG. 1 only in that a lightdiffusion layer 9 is provided on the outside surface of theabsorption-type polarizing film 8.

The light diffusion layer 9 is formed by applying or adhering a lightdiffusion agent on the surface of the absorption-type polarizing film 8.

By this light diffusion layer 9, the reflection on the surface isprevented and at the same time the light reflected by thereflection-type polarizing film 10 is diffused, so that a metallicsilver color is seen, resembling frosted glass, to improve visibility ofa display.

For example, when an absorption-type polarizing film of an anti-glaretype in which silica particles as the light diffusion layer 9 areapplied on the outside surface thereof is used as the absorption-typepolarizing film 8, the metallic silver background becomes a softdisplay, resembling frosted glass.

As a scattering index of the light diffusion layer 9, a Heize value inthe range of 30 to 90 is preferable, and a total light transmittance inthe range of 80 to 90%, which is comparatively high, is preferable.

Third Embodiment: FIG. 6

FIG. 6 is a schematic sectional view showing a structure of the thirdembodiment of the liquid crystal display device according to the presentinvention, which differs from the aforesaid second embodiment only inthat a light diffusion sheet 15 is provided outside the absorption-typepolarizing film 8 in place of the light diffusion layer 9 in FIG. 5.

As the light diffusion sheet 15, used is a sheet in which, for example,adhesives mixed with acrylic beads is applied on a polycarbonate film.Alternatively, a sheet in which embossing is performed on the surface ofa base film or light diffusion particles are dispersed in a base filmmay be used.

As a scattering index of the light diffusion sheet 15, a Heize value inthe range of 30 to 90 is preferable, and a total light transmittance inthe range of 80 to 90%, which is comparatively high, is preferable.

According to the embodiment, the metallic silver background becomes asoft display resembling frosted glass.

Fourth Embodiment: FIG. 7

FIG. 7 is a schematic sectional view showing a structure of the fourthembodiment of the liquid crystal display device according to the presentinvention which differs from the first embodiment shown in FIG. 1 onlyin that a solar cell 21 having a black surface is also used as a lightabsorbing member in place of the light absorbing film 11 made of coloredpaper.

The solar cell is a power source for driving an electronic machinerysuch as a watch which is provided with a liquid crystal display deviceas well as the liquid crystal display device itself and so is disposedunder the reflection-type retardation film 10 of this liquid crystaldisplay device, thereby driving the liquid crystal display withoutdecreasing efficiency of power generation.

As proposed as the modification of the aforesaid first embodiment, thearrangement angle of the reflection-type retardation film 10 is rotatedby 90° so that the background color is displayed in black and theinformation display portion in metallic silver, thereby about 35% ormore of the incident light is absorbed by the solar cell 21 in thebackground portion, which allows the efficiency of power generation tobe sufficient for a digital watch.

Fifth Embodiment: FIG. 8

FIG. 8 is a schematic sectional view showing a structure of the fifthembodiment of the liquid crystal display device according to the presentinvention, which differs from the first embodiment shown in FIG. 1 onlyin that a translucent absorbing film 19 is provided in place of thelight absorbing film 11 made of colored paper and a back light 20 isdisposed outside thereof.

Preferably, a color film is used as the translucent absorbing film 19and an electro-luminescence (EL) light of a plane emitter type is usedas the back light 20, and the combination of a light emitting diode(LED) array and a light guide plate or that of a fluorescent light and alight guide plate can be also employed.

The translucent absorbing film 19 and the back light 20 are provided asabove, thereby the light passed through the reflection-type polarizingfilm 10 is absorbed in the translucent absorbing film 19 in areflection-type display viewed by means of the outer daylight, so thatletters and the like in excellent contrast with the metallic silverbackground caused by mirror reflection of the reflection-type polarizingfilm 10 can be displayed. When a color film is used for the translucentabsorbing film 19, thereby letters and the like which are colored by thecolor film can be displayed on the metallic silver background.

In a dark place such as outdoors at night, the back light 20 is turnedon, which enables a transparent-type monochromatic color display to beclearly performed.

The use of a blue transparent film for the translucent absorbing film 19can creat a blue display, and an optional display color can be obtainedby changing the color of the transparent film.

For example, a gold cholesteric liquid crystal polymer film is used forthe translucent absorbing film 19, which enables a gold metallic displayon the metallic silver background and a display with lighting by theback light 20 in the night.

It should be noted that a color film is used for the translucentabsorbing film 19 in this embodiment, but when the EL light is used forthe back light 20, and the surface thereof is printed in a transparentcolor, thereby the translucent absorbing film 19 can be omitted.

Sixth Embodiment: FIG. 9

FIG. 9 is a schematic sectional view showing a structure of the sixthembodiment of the liquid crystal display device according to the presentinvention. The same numerals are given to the same portions as those inFIGS. 6 and 8.

The sixth embodiment differs from the fifth embodiment shown in FIG. 8only in that the light diffusion sheet 15 is provided outside theabsorption-type polarizing film 8.

The examples, effects and the like of the light diffusion sheet 15 arethe same as those in the third embodiment shown in FIG. 6, therefore thedescriptions thereof are omitted.

Seventh Embodiment: FIG. 10

FIG. 10 is a schematic sectional view showing a structure of the seventhembodiment of the liquid crystal display device according to the presentinvention. The same numerals are given to the same portions as those inFIG. 1.

The seventh embodiment differs from the first embodiment shown in FIG. 1only in that a light diffusion layer 22 is provided between the firstsubstrate 1 of the STN liquid crystal cell 16 and the reflection-typepolarizing film 10.

The light diffusion layer 22 is disposed as described above, thereby adisplay of the metallic silver background also becomes soft, resemblingfrosted glass, so that the same effects as those in the liquid crystaldisplay device of the second embodiment shown in FIG. 5 and the thirdembodiment shown in FIG. 6 can be obtained.

As the light diffusion layer 22, diffusion adhesives in which fineparticles are dispersed in adhesives may be preferably applied on thelower face of the first substrate 1 of the STN liquid crystal cell 16 orthe upper face of the reflection-type polarizing film 10.

Alternatively, the light diffusion sheet 15 may be used similarly to thethird embodiment shown in FIG. 6. The various changes similar to thosein the modifications of the first embodiment are possible in theseembodiments.

Eighth Embodiment: FIG. 11 to FIG. 13

Next, the eighth embodiment of the liquid crystal display deviceaccording to the present invention will be explained hereinafter withreference to FIG. 11 to FIG. 13.

FIG. 11 is a schematic view similar to FIG. 1 showing a structure of theliquid crystal display device of the eighth embodiment, and FIGS. 12 and13 are plane views showing arrangement relations of each axis ofcomponents in the liquid crystal display device. In these drawings, thesame numerals are given to the same portions as those in FIG. 1 to FIG.3 and the descriptions thereof are omitted.

The liquid crystal display device of the eighth embodiment differs fromthe liquid crystal display device of the first embodiment only in thatthe twist angle of an STN liquid crystal cell 17 differs from that ofthe STN liquid crystal cell 16 and a twisted retardation film 14 is usedin place of the retardation film 13 in FIG. 1.

In the STN liquid crystal cell 17 used for the liquid crystal displaydevice of this embodiment, the nematic liquid crystal 7 which is filledand sandwiched in a gap between the first substrate 1 and the secondsubstrate 2 is twistedly aligned at 240°.

More specifically, an alignment film is formed on the surfaces of thefirst electrode 3 and the second electrode 4, a rubbing treatment isperformed so that a lower molecular alignment direction 17 a of liquidcrystal shown in FIG. 12 is disposed in the direction at an angle of 30°counterclockwise with respect to the horizontal axis 30 (0°) on thefirst substrate 1 side, and a rubbing treatment is performed so that anupper molecular alignment direction 17 b of liquid crystal is disposedin the direction at an angle of 300 clockwise with respect to thehorizontal axis 30 (0°) on the second substrate 2 side. Through theabove structure, formed is the STN liquid crystal cell 17 in which thetwisted alignment angle of the nematic liquid crystal 7 is 240°counterclockwise seen from the second substrate 2 side.

A difference Δn in birefringence of the nematic liquid crystal 7 usedfor the STN liquid crystal cell 17 is set to be 0.15 and a cell gap dwhich is a gap between the first substrate 1 and the second substrate 2is set to be 5.4 μm. Accordingly, a Δnd value of the STN liquid crystalcell 17 which is represented by the product of the difference Δn in thebirefringence of the nematic liquid crystal 7 and the cell gap d is 810nm. A twisted pitch of the nematic liquid crystal 7 is adjusted to 11μm.

The absorption-type polarizing film 8 is disposed in such a manner thatthe transmission axis 8 a is disposed in the direction of −45° withrespect to the horizontal axis 30 (0°) as shown in FIG. 13. Furthermore,the twisted retardation film 14 having a Δnd of 620 nm and being twistedat 220° right is provided between the STN liquid crystal cell 17 and theabsorption-type polarizing film 8. A lower polymer molecular alignmentdirection 14 a of the twisted retardation film 14 on the secondsubstrate 2 side shown in FIG. 13 is disposed in the direction of 55°counterclockwise with respect to the horizontal axis 30, and an upperpolymer molecular alignment direction 14 b of the twisted retardationfilm 14 on the absorption-type polarizing film 8 side shown in FIG. 13is disposed at an angle of 850 clockwise with respect to the horizontalaxis 30. The reflection-type polarizing film 10 is disposed under theSTN liquid crystal cell 17 in such a manner that the transmission axis10 a shown in FIG. 12 is parallel to the horizontal axis 30. Moreover,under the reflection-type polarizing film 10, disposed is the lightabsorbing member 11 such as a sheet of colored paper.

As the twisted retardation film 14, it is preferable to use a liquidcrystal polymer film in which an alignment treatment is performed to aTAC (triacetyl cellulose) film with 80 μm in thickness, the film iscoated with liquid polymer and is cured by quickly cooling afteradjustment so as to be at a required twisted condition at hightemperatures of 100° C. or more.

The twisted retardation film 14 has a twist in the reverse direction tothe twist direction of the STN liquid crystal cell 17 compared with theordinary retardation film used in the aforesaid embodiments, so thebirefringence occurred in the STN liquid crystal cell 17 can becompletely compensated.

The components shown in FIG. 11 are adhered to each other with acrylicadhesives. Other structures are the same as those in the aforesaid firstembodiment.

In a state with no voltage applied on the STN liquid crystal cell 17,the light linearly polarized in the direction parallel to thetransmission axis 8 a which is incident from the absorption-typepolarizing film 8 assumes an elliptically polarized state after passingthrough the STN liquid crystal cell 17 in the case of no twistedretardation film 14, thereby it is unnecessarily colored by thereflection-type polarizing film 10 or can not pass through as acompletely linearly polarized light, and there is a possibility that thedisplay becomes insufficient in quality.

However, the twisted retardation film 14 is disposed between theabsorption-type polarizing film 8 and the STN liquid crystal cell 17, sothat the linearly polarized light incident through the absorption-typepolarizing film 8 into the twisted retardation film 14 assumes anelliptically polarized state.

The elliptically polarized light is compensated while passing throughthe STN liquid crystal cell 17 to become a substantially completelylinearly polarized light, rotates right about 45° clockwise with respectto the transmission axis 8 a of the absorption-type polarizing film 8,and emits from the position at 90° with respect to the horizontal axis30 in FIG. 13.

The transmission axis 10 a of the reflection-type polarizing film 10 isdisposed, as shown in FIG. 12, parallel to the horizontal axis 30, sothat the light linearly polarized in the direction orthogonal to thetransmission axis 10 a reaches the reflection-type polarizing film 10.Accordingly, as shown in the off-state in FIG. 4, the whole incidentlight is reflected by the reflection-type polarizing film 10, whichappears as a metallic silver background.

In an on-state when voltage is applied across the first electrode 3 andthe second electrode 4 of the STN liquid crystal cell 17, molecules ofthe nematic liquid crystal 7 rise, the birefringence of the STN liquidcrystal cell 17 changes, and the emitting linearly polarized lightrotates about 90° to be in the direction parallel to the horizontal axis30.

Accordingly, the linearly polarized light passed through the STN liquidcrystal cell 17 reaches the reflection-type polarizing film 10, parallelto the transmission axis 10 a thereof, and therefore all passes throughthe reflection-type polarizing film 10 and is absorbed in the lightabsorbing film 11. If the color tone of the light absorbing film 11 isblue, blue light is reflected, thereby the display can be seen as a bluecolor.

Therefore, blue letters and figures are displayed in high contrast onthe metallic silver background.

The liquid crystal display device is applied to, for example, a displayportion of a fashion digital watch, which can provide a quite colorfuldigital watch in combination with a case or a band.

The various changes described as the modifications of the firstembodiment are similarly possible in the eighth embodiment.

Ninth Embodiment to Fourteenth Embodiment: FIG. 14 to FIG. 19

FIG. 14 to FIG. 19 are schematic views similar to FIG. 5 to FIG. 10showing the ninth embodiment to the fourteenth embodiment of the liquidcrystal display device according to the present invention respectively.

In each embodiment, the liquid crystal display device using the STNliquid crystal cell 17 and the twisted retardation film 14 similar tothose in the eighth embodiment shown in FIG. 11 has an additionalconfiguration similar to that in the second embodiment to the seventhembodiment shown in FIG. 5 to FIG. 10 respectively.

These configurations and effects are the same as those of the secondembodiment to the seventh embodiment shown in FIG. 5 to FIG. 10, exceptthe differences from those of the first embodiment shown in FIG. 1 andthe eighth embodiment shown in FIG. 11, therefore the descriptionsthereof are omitted.

The various changes described as the modifications of the firstembodiment are similarly possible in these embodiments.

INDUSTRIAL APPLICABILITY

As it is obvious from the aforesaid description, in the liquid crystaldisplay device according to the present invention, display ofinformation with letters and figures in black or an optional color on ametallic silver background can be performed with high contrast, andthereby a monochromatic color display with an excellent visible anglecharacteristic and richness in designs is possible.

As a result, the liquid crystal display device can be used as a displaydevice in various electronic devices including a portable electronicdevices such as a wrist watch, a portable telephone or the like, andincreases the visibility thereof. Moreover, it can provide colorfulelectronic devices rich in designs.

1. A liquid crystal display device, comprising: a super twisted nematicliquid crystal cell in which nematic liquid crystal having a twist anglein the range from 180° to 270° is filled and sandwiched between atransparent first substrate having a first electrode and a transparentsecond substrate having a second electrode; a twisted retardation filmprovided outside said second substrate; the twist angle and the Δndvalue of the twisted retardation film are smaller than that of the supertwisted nematic liquid crystal cell; an absorption-type polarizing filmprovided outside the twisted retardation film for absorbing lightlinearly polarized in the direction orthogonal to the transmission axisthereof; a reflection-type polarizing film having a transmission axisand a reflection axis in a direction orthogonal to the transmissionaxis, provided outside said first substrate for transmitting lightlinearly polarized in a direction parallel to the transmission axis andreflecting light linearly polarized in the direction parallel to thereflection axis; and a light absorbing member provided outside thereflection-type polarizing film, wherein said twisted retardation filmand said reflection-type polarizing film constitute reflection lightincreasing means which increases intensity of reflected light which istransmitted from a visible side of said super twisted nematic liquidcrystal cell and reflected to the visible side by said reflection-typepolarizing film in which light changed into elliptically polarized lightwhen transmitted through said absorption-type polarizing film and saidtwisted retardation film from the visible side is set to return tosubstantially linearly polarized light and outputted after furthertransmitted through said upper twisted nematic liquid crystal cell toincrease brightness of said reflected light in a state no voltage isapplied to the liquid crystal cell, while the light enables the color ofsaid light absorbing member to be visible in a state voltage is appliedto the liquid crystal cell.
 2. The liquid crystal display deviceaccording to claim 1, wherein a light diffusion layer is provided on theoutside surface of said absorption-type polarizing film.
 3. The liquidcrystal display device according to claim 1, wherein a light diffusionsheet is provided outside said absorption-type polarizing film.
 4. Theliquid crystal display device according to claim 1, wherein saidabsorption-type polarizing film is a color polarizing film using adichromatic pigment.
 5. The liquid crystal display device according toclaim 1, wherein said light absorbing member is a color filter.
 6. Theliquid crystal display device according to claim 1, wherein said lightabsorbing member is a solar cell.
 7. The liquid crystal display deviceaccording to claim 1, wherein said light absorbing member is atranslucent absorbing member and a back light is provided outside thetranslucent absorbing member.
 8. The liquid crystal display deviceaccording to claim 1, wherein a light diffusion layer is providedbetween said first substrate of the liquid crystal cell and saidreflection-type polarizing film.